The study evaluated the water quality of Baiyangdian Lake from 2003 to 2009. Main pollutants were COD and TN, with DO levels good except in Nanliuzhuang. Nanliuzhuang had higher water quality than other sites near the Fu river. Zaolinzhuang and Duan village had better water quality than other sites. Water quality at outlets was better than inlets. Water quality slightly improved in Nanliuzhuang from 2003 to 2009, but overall water pollution worsened. Self-purification improved at other sites. Reasons for water quality deterioration were discussed, and protective and treatment measures were suggested.